Electrical instrument



1927. June 'r. L..LEE

ELECTRICAL INSTRUMENT Filed April 4, 1925 Fig. 11

Hnwentor: DWI. t 1-9.;

Patented June 14,1927.

UNITED STATES PATENT OFFICE.

THOMAS L. LEE, OF ROCHESTER, NEW YORK, ASSIGNOR TO NORTH EAST ELECTRICCOMPANY, OF ROCHESTER, NEW YORK, A CORPORATION OF NEW YORK.

ELECTRICAL INSTRUMENT.

Application filed April 4, 1925. Serial No, 20,781.

' This invention relates to electrical instruments, such as voltagecontrolling relays and the like, in which magnets and electro- 'magneticwindings are used. In some such instruments it is desirable tocompensate for the effect of temperature upon the windings, and it hasbeen proposed to accomplish thls by the use of a magnetic shunt carryinga part of the flux and consisting of material such, for example, ascertain nickel-steel alloys, having a pronounced temperature coefliclentof permeability substantially different from that-of. the iron or steelconstituting the principal portion of the magnetic circuit. A

In the manufacture of instruments such as just described, it has beenfound difficult, owing to unavoidable variations in manufacture and inthe characteristics of the compensating alloys used, to secureinvariable results in the use of such alloys, While such variations maybe met by changing the thickness or extent of the bodies of compensatingmaterials employed, this is not convenient when manufacturing in largequantities. The object of the present invention, therefore, is toprovide a simple and eflecthe means for adjusting the efi'ect or" themagnetic shunt without introducing variations in the dimensions of thebody of shunt material. I have found that this may be a'ccomplished bythe use of a readily exchangeable body of magnetic material, of adiflerent temperature coefi'icient and of less extent than the shunt,which is applied to the latter in such a way as, in effect, topartiallyshort circuit the latter in so far as the flux-path is concerned.

P The invention, accordin ly, consists in the construction hereinafterescribed, as it is defined in the annexed claims.

In the accompanying drawings, Fig. aside-elevation, partly in section.of an instrument embodyin the present invention. Fig. 2 is a sectlon lplan-view of the line 2-2 in Fi 1; and Fig. 3 is a plan-view of a series0 interchangeable adjusting members suitable fpr use in the instrumentshown.

The invention is illustrated as embodied in an instrument having acylindrical magnetic core 5 of steel, surrounded by a winding 6. Anarmature 7 cooperates with the core and is ivotally mounted upon whatmay be descri edas the yoke-member 8 of the instrument. The member 8completes shell, to the lower end of which the core 5 is fixed. Thearmature 7 controls contacts 9 and is itself controlled by a spring 10.

The details of construction just described are not in themselvesessential to the invention, as the magnetic circuit, and theconstruction of the armature, the contacts etc., may take widelydifierent forms consistently therewith.

The compensating shunt, as illustrated, has the form of a rectangularplate 11, which may conslst of some material such, for example, asnickel-steel, having a pronounced negative temperature coeflicient ofpermeab1l1ty. ThlS plate is perforated to surround the upper polarextremity of thecore 5, and 1s secured to the yoke 8 by means of a bar12 of any convenient material. The efl'ect of this shunt is toshort-circuit a part ofthe magnetlc flux which would otherwise passthrough the armature, and since the efiicacy of the shunt diminisheswith rise in temperature, .it thereby tends to compensate for theincrease of resistance which occurs at the same time in the winding 6.

The adjusting device characteristic of the present lnvention is shown ashaving the form of a perforated disc or washer 13, which may be of ironor steel, and which surrounds the core and lies upon the upper surfaceof the shunt 11. means tor securing the washer 13 in place, the core isprovided with an annular groove, and a split rin 14 or spring wire liesin th s groove an engages and retains the washer.

in the manufacture of instrumentssuch asjust described, a quantity ofwashers 13 may providedhavin several different diameters, as shown inig. 3. The compensating shunt will be designed to have a somewhatexcessive compensating eflect, so as to overcompensate the instrument.After the instrument has been assembled, without the adjusting washers,it may be tested and the exact de cc of overcompensation ascertained. ymeans of a table or formula, an

As a convenient adjusting washer 13 of the correct diameter analternative path, oi relatively high e m-k meability, for a portion ofthe flux w ch would otherwise pass throughthe compensator, and thus, inefiiect, diminishes the length of the flux path through the compensating material.

While the Washer 13 provides a' device, or the purpose in question,which is convenient and inexpensive in form, it will he understood thatthis adjusting member may have various forms suitable for instruments ofvarious designs in which it may he used.

The invention claimed is:

1. In an electrical instrument, the com-. bination, with a magnet, of acompensating magnetic shunt consisting of metal having a pronouncedtemperature coefiicient of permeability; and means'for adjusting theetfeet of said shunt, comprising a body of magnetic material, ofdifferent temperature COGlfiClGDt, rei'novahly attached to said shuntand of less extent than the shunt,

2. In an electrical instrument, the combination, with the core of anelectromagnet, and a compensating magnetic shunt consistlng of a platesurrounding a polar extremity of the core and consisting of metal havinga pronounced temperature coefiicient of permeability, of means, foradjusting the effect of said shunt, consisting of a Washer, of magneticmaterial, lying upon said shunt and attached to the core' 3'. In anelectrical instrument, the combination, with the core of anelectromagnet, and a compensating magnetic shunt surrounding a polarextremity of the core and consisting of metal having a pronouncednegative temperature coefficient of permeability, of means, foradjusting the eitect of said shunt, consisting of a plate of magneticmaterial, of less extent than said shunt, and means for securing saidplate removahly to the cor in engagement with the shunt.

THOMAS L. LEE.

